Lug wrench

A lug wrench is the name for a type of socket wrench used to loosen and tighten lug nuts on automobile wheels. In the United Kingdom and Australia, this tool is commonly known as a wheel brace.

Lug wrenches may be L-shaped, or X-shaped. The form commonly found in car trunks is an L-shaped metal rod with a socket wrench on the bent end and a prying tip on the other end. The prying tip is mainly intended to remove hub caps or wheel covers that may be covering a wheel's lug nuts.

Another common type, sometimes called a spider wrench, is made in the shape of a cross with different sized sockets on each of the four ends.

Technique

Ideally, the nuts (or bolts) should be tightened with a torque wrench. Lug wrenches are much less expensive because they lack the ability to measure or limit the force used. Installing a wheel with a lug wrench thus requires a bit of rough guessing about proper tightness. Excessive force can strip threads or make the nuts very difficult to remove. Also, uneven torque between the various lug nuts, or excessive torque, can lead to warping of the brake rotor if the car is equipped with disc brakes. For this reason, impact wrenches should properly be used only for removing lug nuts, not for tightening them, although in practice this rule is often ignored for convenience's sake, even by professional mechanics.